In the confectionary industry, products are manufactured comprising a core, and an outer coating or shell covering the core.
More specifically, candies are manufactured comprising a core, preferably formed by compacting powdered substances containing sugar, flavourings and excipients; and a hard, compact, sweet outer shell varying in thickness according to the type of product.
The shell is formed in machines comprising a rotating drum, in which the cores for coating are tumbled continuously and alternately sprayed periodically with sweet syrup and flavourings. After each syrup spraying, the cores are dried by blowing hot air through the drum to remove moisture from the syrup and leave a film on the cores. The number of spray and dry cycles depends on the desired coating or shell thickness, which is considerable, especially in candies in which the shell weighs almost as much as the core. In which case, the coating process is a long, time-consuming job, which limits the extent to which output can be increased.
Moreover, the known coating method makes it extremely difficult to maintain the organoleptic quality of the sprayed products and particularly the flavourings. That is, the products are both sprayed and dried in a high-temperature, oxygen-containing environment, normally of over 60° C., which inevitably initiates degradation of the flavourings; and reducing the temperature by reducing the temperature of the drying air only further increases cycle time.